The present invention relates to a thin film device which uses a hydrogenated amorphous silicon (a-Si:H) thin film, and more particularly to a thin film device having a high resistance region.
FIG. 1 shows a circuit diagram of a prior art matrix driving contact type linear sensor array (see U.S. Pat. No. 4,369,372 or Japanese Utility Model Application Laid-Open No. 53,760/82). In FIG. 1, numeral 101 denotes a blocking diode used for switching of matrix drive, numeral 102 denotes a photo-diode for photo-electric conversion and numerals 103 and 104 denote drive terminals. The blocking diode 101 and the photo-diode 102 are PIN-junction diodes formed in a common process using amrophous silicon and have a current versus voltage characteristic as shown in FIG. 2. A forward current rises at approximately 0.6 V, and in a backward direction, a break-down occurs at approximately -50 V. When a static electricity having a voltage larger than the break-down voltage V.sub.B is applied to the diode in the reverse direction, the I-layer is broken and the PIN-junction diode is shorted, as experimentarily provided. In handling the sensor of FIG. 1, if the terminal 106 is touched by a charged hand while the terminal 105 is connected, a current flows along a path shown by an arrow and the blocking diode 108 and the photo-diode 110 which are device-biased are broken while the forward-liquid photo-diode 110 and blocking diode 111 are not influenced.
A potential of a human body charged by chemical texture reaches up to 10,000 V. If a hand of a worker charged to such a high potential contact to the terminal 106, a number of picture elements (comprising combination of blocking diodes and photo-diodes) are broken by the path shown and a yield in the test of the device or mounting to apparatus is significantly lowered.